Explanation:
just add all the given angles and equate it with 540° and then find x
x/2 + x/2 + x - 25 + 100 + x - 15 = 540°
3x + 60 = 540°
3x = 540 - 60
x = 480/3
x = 160°
on checking, the given shape values of x-25 and x - 15 are both still obtuse angles thus the answer is correct.